The present invention relates to waterjet propulsion of a marine vessel, more particularly to methodologies for designing, in furtherance of waterjet propulsion of a marine vessel, a configuration including a flush inlet and a portion of a marine hull.
The design of a flush inlet for a ship with jet propulsion has traditionally been approached in an ad hoc fashion, lacking analytical procedures that relate geometric parameters to the design predictions. In particular, these conventional methodologies fail to take into consideration the influence of the ship hull on the flush inlet performance and vice versa.
The inlet performance is critical to the success of a waterjet propulsion system. There are major effects associated with inlet-hull interactions. First, the inlet, in conjunction with the hull, constitutes an important hydrodynamic interaction problem that can greatly affect the drag characteristics of the ship. The drag can either be reduced or augmented relative to the hull without inlet. The inlet flow can also affect the trim of the ship and subsequently the drag. The location of the inlet on the ship hull is an important consideration for the drag problem.
The inlet also changes the hull flow characteristics in the vicinity of the inlet. The flow inside the inlet can be subject to adverse pressure gradient, and flow separation can be prominent if no systematic method is available to relate flow characteristics to geometric parameters. The stagnation flow near the lip region of the inlet is critical for good cavitation performance.
In addition, the inlet geometry has a significant effect on pump performance. The proper shaping of the inlet is important to have minimum dynamic head losses in the flow passage, due both to turning and to frictional losses at the wall. The flow in front of the pump face needs to be as uniform as possible to minimize unsteady flow behavior of the pump. The interactions between the inlet and hull must be favorable to propulsion without inducing flow separation and/or cavitation.
The following United States patent documents, hereby incorporated herein by reference, are of interest as pertaining to waterjet propulsion of marine vessels: McBride, “Mixed Flow Pump,” U.S. Patent Application Publication No. US 2003/02228214 A1 published 11 Dec. 2003; Burg, “Marine Vehicle Propulsion System,” U.S. Pat. No. 6,629,866 B2 issued 7 Oct. 2003; Burg, “Waterjet Propulsor for Air Lubricated Ships,” U.S. Patent Application Publication No. US 2003/0154897 A1 published 21 Aug. 2003; Burg, “Augmented Waterjet Propulsor,” U.S. Patent Application Publication No. US 2002/0127925 A1 published 12 Sep. 2002; Burg, “Marine Vehicle Propulsion System,” U.S. Patent Application Publication No. US 2002/0052156 A1 published 2 May 2002; Shen et al., “Steering and Backing Systems for Waterjet Craft with Underwater Discharge,” U.S. Pat. No. 6,171,159 B1 issued 9 Jan. 2001; Chen et al., “Tractor Podded Propulsor for Surface Ships,” U.S. Pat. No. 5,632,658 issued 27 May 1997; Dai et al., “Hull Supported Steering and Reversing Gear for Large Waterjets,” U.S. Pat. No. 5,591,057 issued 7 Jan. 1997; Peterson et al., “Compact Water Jet Propulsion System for a Marine Vehicle,” U.S. Pat. No. 5,476,401 issued 9 Dec. 1995; Chen et al., “Torque Balanced Postswirl Propulsor Unit and Method for Eliminating Torque on a Submerged Body,” U.S. Pat. No. 5,445,105 issued 29 Aug. 1995; Stricker, “Transverse Waterjet Propulsion with Auxiliary Inlets and Impellers,” U.S. Pat. No. 4,531,920 issued 30 Jul. 1985; Johnson, Jr. et al., “Movable Ramp Inlet for Water Jet Propelled Ships,” U.S. Pat. No. 3,942,463 issued 9 Mar. 1976.